A push-button is a very simple control means which consists schematically of a stem sliding in a passage through the frame of a device, while being held in a rest position by elastic means which push the head of the stem outwards, and being moved into the operating position by the user pressing on the head. The elastic means are, for example, formed by a helical spring housed inside the through passage and which is supported between the frame and the push-button head.
In applications where it is easy for the user to see whether a device is operating properly, such as lighting a chamber or activating a sound source, a control means of the aforementioned type may be satisfactory, even in its simplest form. In other cases, however, it is necessary for the user who presses on a push-button to feel certain that the selected function has actually been activated, in particular when he is not in a position to perform a visual or auditory check. This is particularly so in a chronograph watch, regardless of whether it is mechanical or electronic. Indeed, the command to start/stop timing by pressing on an appropriate push-button must be synchronized with an event, for example a sporting event, that the user has to watch, which means that he cannot simultaneously visually check that the chronograph is operating properly.
To overcome this drawback, various devices have been proposed for producing a click that can be felt by the user when he presses on a push-button. Purely by way of example, the elastic means that are used to hold the push-button at rest may consist of an elastic strip, whose first free end is fixed on a plate and whose second free end, used to hold the push-button in a rest position, is extended by a curved U-shaped portion substantially in the axis of the push-button. This curved portion, which is also elastic, bears against a stud pressed into the plate and, at the end thereof, presents a thickened portion or a notch which, as it passes over the stud, produces a click when the push-button is pressed.
Depending on whether the chronograph watch is mechanical or electronic, activating the push-button will cause a timer mechanism to start or will cause an electrical contact to close just after the click is felt. The drawback of such a push-button arrangement lies, however, in its size, which is relatively large given that the elastic strip extends into a plane and must be sufficiently long to be able to transmit the force applied by the user on the push-button while remaining elastic.
The present invention concerns a second type of so-called surface mount push-button also known as a surface mounted device or SMD. The actuator element of this type of push-button typically consists of a dome-shaped flexible metal sheet, the dome presenting a periphery that bears on a first contact and a peak which, when the user presses on the push-button, deforms and bears on a second contact, which closes an electrical contact and sends an electrical control signal. When pressure is applied to the push-button, the dome changes from its rest position to a pressed-in position, producing a click which is felt by the user. One of the advantages of surface mount push-buttons is that they occupy less space and can therefore be incorporated in devices of small dimensions.
It will be understood, however, on examining FIG. 1 annexed to the present Patent Application, that when such a push-button 1 is mounted on an electronic plate 2 housed inside the case 4 of a portable object, such as an electronic or electromechanical wristwatch, it is often actuated through the side of case 4, i.e. along a radial line therefrom. However, as is noted in FIG. 1, the substantially L-shaped support 6 for push-button 1, is mounted in a cantilever fashion via one of its branches 6a on the upper surface 8 of electronic plate 2 by means of a few weld spots 10. Depending on how good the quality of weld spots 10 is, the second branch 6b almost inevitably has a slight play 12 with side surface 14 of electronic plate 2, so that under the effect of shear forces due to repeated applications of pressure on push-button 1, there is a high risk of weld points 10 yielding due to fatigue.